amenjet wrote: ↑Wed Mar 06, 2024 7:04 pm
I agree. You can use parts from ebay but you do need to know what to look out for. The big advantage with the RS type sellers is a datasheet for everything and always as good quality as anywhere else or better. You pay for it though...
Maybe the way to handle this is to buy the RS components at higher quantity and split the components into 'Whine Fix Kits'?
One thing I found when I did some of these fixes is that a desoldering tool is useful. The caps didn't really want to be removed easily and the PCb can be damaged by rough removal.
The whine-fix idea is good. RS sell the small 'FR series' caps needed, in sets of 10, likely for all relevant values, so the outlay isn't big. LePowerfulPierre (Sourcerer), being a man who sounds like a man used to pulling locomotives with his teeth, might find the haulage light enough. It's an ideal thing for someone already trading Psion gear to do, possibly. :)
As you say, getting the old caps out and the new ones in can be difficult. I used to use a desolder but those can prang the already hot copper pads and cause them to lift. In very confined spaces this method isn't possible at all. Braid can be awkward too. The method I use will scale up to hundreds of caps with reliability at 100%. I've repaired many Mini-ITX boards this way, where the room for manoeuvre can be extremely small.
Method:
1: Note cap position and polarity, then grasp the body with long-nose pliers, carefully pulling on it so the body comes away from the pins, which stay in the board. 'Walk' it from pin to pin while maintaining tension, if it's tough to grip it. (No squashing, that would just trap the pins in the cap).
2: Desolder each pin, pulling it away with the pliers, leaving the solder in place afterwards. Remove just enough to get a centred pit for drilling.
3: Use a cheap 'pin drill', with the supplied 0.7mm collet chuck and a 0.7mm drill bit, to manually drill out the solder. Use a light pressure and spin it moderately fast by hand till it goes through. Brush away debris.
4: Fit the new capacitor, maintaining its position by a tiny dab of superglue, or by bending the leads outward slightly.
5: Solder it in with thin resin-cored solder and trim the leads.
This method might need a couple of practise attempts on an old PCB so you get used to any awkwardness involved, but it's worth it because it's 100% effective, and can be repeated as many times as you'll ever need, unlike any method that damages the tracks or pads. The pin drill and bit are likely cheaper than a desolderer of any worth, and the waste lead (Pb) is much lower than any method that uses full desoldering. If through-hole boards are to be handled, then it may be better to use a 0.6 mm drill in the 0.7mm chuck, and to make sure by twisting a few times, that it runs free once it's drilled through. This will make a hole big enough for the lead while avoiding any damage to the plating in the hole, because that plating will always be harder, and of greater diameter, than the plug of solder the drill will be removing. Residual solder will protect the plating and give a firm guide to the new capacitor's leads when fitting it.
This may sound tedious, but it's not, it's the only method I can trust after the hundredth pin in a long session, I'd get tired and likely damage something with a desolderer, but drilling out the solder is much easier and safer. It reduces the time for exposure to harmful vapours too.